Hello Peter,
No, the frequency is given by the transmitter site, not by the Opera
software. The bandwidth of a VLF antenna is usually very small and
there is a lot of effort to tune the system to resonance. Since most
grabbers are running at 8.97 kHz and since even lower freqencies mean
an even more lower antenna efficiency, it is useful to stay as close as
possible below 9 kHz.
Unfortunately Opera as well as WSPR does not offer a wide frequency
input range, e.g. 0...24 kHz for the standard soundcard samplerate of
48 kS/s. Actually that should be no problem but most of the programmers
obviously cannot imagine (although often explained) that there are
other receive systems then a usual HF TRX with a SSB AF filter
(0.3...2.8 kHz). However, there are several stations on LF (e.g. TF3HZ,
G4WGT, DM4TR, DK7FC, DF6NM, YV7MAE, Edgar.J. Twining, SV8CS,
YO/4X1RF........) and MF, VLF anyway, who doesn't use a HF receiver.
Those stations are then forced to use SpecLab and VirtualAudioCable
software to convert the incoming AF to the 100 (200) Hz wide AF range
needed for the program.
BUT: DF6NM's OPDS software uses SpecLab anyway. So here, the problem
does not exist :-)
If you actually want to use the normal Opera software for VLF (remember
the 10 dB lower decode performance against OPDS), either OP32 or OP4H,
i recommend to do it as we all have to do and use SpecLab and VAC to
convert the 8970 Hz tone to the needed frequency, e.g. a frequency
shift / down conversion of 70 Hz.
Here the WX was fine, the WX forecast was wrong :-/ I intend to run an
experiment this weekend, if the WX permits.
73, Stefan/DK7FC
Am 27.12.2013 13:57, schrieb PA1SDB, Peter:
Hello VLF,
Opera RX on 8KC, 24/7 now.
Also Spectogram available.
The frequency band is 8895 - 8925 Hz,
right ?
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